Budget airline Ryanair may no longer have to pay back a euro4.5 million ($6.16 million) subsidy to the Belgian state after a court ruled Thursday against an EU order to refund the sum.

The European Union's appeals court said antitrust regulators made mistakes when they ordered Ryanair to pay back the public money it got to help it run flights from Charleroi airport in the southern Belgium region of Wallonia.

The EU Court of First Instance said the European Commission should have looked at whether the money from Belgian state companies could be seen as a normal market investment — and not state help.

Charleroi was granting the airline up to 90 percent of its costs over 15 years in a deal the Irish airline has mimicked with small airports across Europe.

Ryanair said the court ruling backed the airport's business model of attracting business with low charges for favored airlines. It called on regulators to drop similar subsidy investigations at eight other airports that Ryanair uses.

Ryanair Holdings PLC, Europe's largest low-cost carrier, triggered a revolution in air travel by offering bargain fares that saw millions more Europeans take to the skies — even if that meant an hour-long trip from a regional airport to their city destination.